Strip-shaped Co3O4 as a peroxidase mimic in a signal-amplified impedimetric zearalenone immunoassay.

An impedimetric immunoassay was designed for ultrasensitive determination of zearalenone (ZEN). It is making use of the peroxidase-like activity of strip-shaped Co3O4 (ssCo3O4) which catalyzes the oxidation of 4-chloro-1-naphthol to produce an insoluble precipitate in the presence of H2O2. The precipitate is electrically nonconductive and accumulates on the electrode, thereby retarding the electron transfer from the redox probe ferro/ferricyanide to the surface of electrode. This amplifies the impedimetric signal in accordance with logarithm of the concentration of ZEN. The electrode was further modified with TiO2 mesocrystals (TiO2 MCs) which improve the capture of more analytes and increase the performance of the immunoassay. Under optimized experimental condition, the impedimetric signal increased linearly with the logarithm of the ZEN concentration range between 0.1 fg·mL-1 to 10 pg·mL-1. The detection limit is of 33 ag· mL-1. Graphical abstractThis work describes an impedimetric immunoassay based on the use of strip-shaped Co3O4 that catalyzes the production of an insoluble precipitate in the presence of H2O2 on the surface of a glassy carbon electrode. The effect was used for signal amplification in an electrochemical immunoassay for zearalenone.